Method of trapping particles in suspension in gas-currents.



Patented Sept. 23, 1913.

T. E. MURRAY L C. B. GRADY.

APPLICATION FILED JAN.9, 1913.

i IL- iff' l I" l l l l l l I 1 t METHOD 0F TRAPPING PARTICLBS 1NSUSPENSION 1N GAS CURRBNTSA prin THOMAS E. MURRAY AND SATS 'PATE'IMETHOD OF TRAPPING PARTICLES IN SUSPENSION IN GAS-CURR-ENIS.

Application filed January 9, 1913.

Specification of Letters Patent.

Patented Sept. 23, 1913. Serial No. 740,946.

To all whom it may concern.' y

Be it known that we, THOMAS E. MURRAY and CHARLES B. GRADY, citizens ofthe United States, residingy at New York, in the county of New York andState of New York, have invented a certain new and useful Improvement inMethods of Trapping Particles in Suspension in Gas-Currents, of whichthe following a specification.

The problem which we have solved is to entrap the maximum percentage ofsolid particles entrained with and suspended in a gas current. Thisproblem presents itself in the arts under many and different conditions.Those under which we have encountered it and which are therefore dealtwith herein as typical, arise from the need which exists especially incities and densely populated areas, of preventing the discharge ofcinders and other solid matter in comminuted form from chimneysconnected to boiler Haes-especially when forced draft iS used and whenchanges in the load demand the driving of the boilers to varying' limitsoften much beyond their ratingsl This is especially the case when theboilers furnish the power for electriclighting installations, thedemands upon them then varyingV at different periods of the day, andsometimes suddenly increasing. The gas currents in the flues then varygreatly in velocity, with corresponding variations in the quantity ofsolid matter entrained.

We provide a body of liquid, preferably Water, which receives andretains the particles project/ed upon it. We project the stream ofparticles vertically downward f* upon the surface of said liquid.-

When the ,qas current varies in velocity, we vary the cross sectionalarea of the delivery outlet proportionately to said veloc-` ity, so thatas this velocity decreases, the area will decrease, and as the velocityincreases, the area will increase, thus neutralizing the effect of thevelocity changes in the current in the lue. If, therefore, at theoutset, and for some selected velocity of flue current, the intervalbetween the delivery outlet and the liquid level be chosen which willbe, on the one`hand, sutliciently large not to impose a constriction inthe path of the escaping gases, and, on the other, not too greatmaterially to diminish the inertia of the projected particles beforethey strike the liquid, then it is obvious that no matter whatconditions arise in the boilers capable of changingthat velocity, bysuitably varying' the velocity of the projected jet, we can maintain thcadvantageous status previously decided upon, or, in other words,eliminate the etl'ccts of the varying conditions.

In addition to varying the escape outlet, we may also vary the intervalbetween the level of the liquid and said outlet or point of projectionof the particles proiuntionately to the change in area of said outlet.lVhen the liquid level is brought nearer the discharge outlet, the jetof projected particles will strike the liquid with ,greater energy thanbefore, will, therefore, more deeply penetrate it, and so will becomemore etliciently trapped.

Vire have invented a method and an apparatas for carrying said methodinto practical effect.

Our present invention is the method, more particularly set forth in theclaims.

In another application for Letters Patent, Serial No. 740,947simultaneously tiled herewith, we have setl forth said apparatus and instill another application, Serial No. 770,305, tiled May 28th, 1013, wehave claimed the method of trapping solid particles in suspension in agas current of varylng velocity which consists in projecting saidparticles in a direction normal to and upon the surface of a body ofliquid, and maintaining the velocity of said particles at their point ofprojection substantially constant.

In the accompanyingr drawings-Figure 1 is a section of our apparatus onthe line m, w of Fig. 2. Fig. 2 is a section on the line y, jz/ ofFig. 1. Fig. 3 shows the relations of the discharge orifice and thewater level as in Fig'. l, but on a larger scale.

Similar letters of reference indicate like parts.

A is a flue, leading from any source of gas current, wliiclrentrains insuspension the solid particles which are to be trapped. Such particles,for example, may he cinders, flue dust, ash, unconsumed carbon, or anyother connninuted material present in the gas current in the flue of asteam boiler. The flue A connnunicates with an enlarged flue B, throughthe top wall C thereof. 011e end of flue B is closed bv wall D. The

-to the drum K,

other end, shown broken 0H, in practice communicates with a chimney orother escape conduit. At the bottom of the Hue B is a tank E for holdingwater. Said tank is preferably made of cement, or other material, whichwill resist the attack of such acids as may be formed by the gascombining with said Water. Within the Hue B and terminating at itslo-wer edge, below the horizontal plane coinciding with the water levelin the tank E, is a narrow vertical partition F.

G is a swinging plate extending between the partition F and end wall D.Said plate is hinged to the upper wall ofv Hue B in any suitable way. Ashere shown, it has a hooked upper edge H which is received upon theWater supply pipe I, which pipe is supported on the under side of thetop wall C. The swinging plate G, the longitudinal wall J of Hue B, theend wall D, and the fixed partition F, form a substantially funnelshapedcontinuation of the Hue A, which terminates above the liquid level intank E, so that the solid particles escaping at the outlet a, Fig. 3, ofsaid continuation are projected upon the liquid in a direction normal tothe liquid surface. It will be obvious that by swinging the plate Gnearer to the wall J, the area of said outlet a will be diminished, andby swinging the plate G farther fromthewall J, the area of said outlet cwill be increased. ln order to swing the plate G for the 4purpo-se ofadjusting said outlet area, we here show a drum K mounted in brackets Lon the exterior of wall J, and connected to plate G by a chain passingthrough said wall. Said drum is turned by the crank handle M, and isprovided with a pawl and ratchet N, whereby the plate G is held inadjusted position.

The water supply to tank E is preferably admitted in a constant andregulated How from the pipe O, communicating with any suitable source,which pipe connects by pipe P with the pipe I. The pipe I is perforatedand is located at the top of plate G, so that a sheet of water Q. Howsdown the inner side of plate G and into the tank E. This stream may beregulated by the valve R, in pipe P.

Water Hows from the tank E by the pipe S located near the bottom thereofand provided o-utsi-de the tank with a hinged section T. Said section isconnected by a cha-in to the drum K. VThe function of the pipe -sectionT is to adjust the Water level in tank E, said level being raised whenthe pipe section is raised and lowered when sai section is lowered. Thechains from the swinging plate G and the pipe section T are connected sothat when the drum is rotated, t-he plate and the pipe section will bemoved or be permitted to move simultaneously. l-lence, for example, whenthe area. of the outlet a is reduced, the water level in tank E is,correspondingly raised from the line L to the line c, Fig. 3.

The operation is as follo-ws: The gas current holding the solidparticles in suspension enters the top of Hue B between the swingingplate G and wall J and passes downwardly, meeting the descending waterstream Q. The current then escaping' through the outlet a, the solidparticles are projected downward upon the surface (indicated by line c,Fig. 3) of the Water in tank E. The gas passes thro-ugh the interval dbetween the lower end of the swinging plate G and the liquid surface c,and then travels through the Hue B to the chimney or other outlet. Thedownward projec- Vso tion of the particles is assisted by the water lstream Q, delivered into them. The particles after striking the water intank E, enter the same and so become trapped. Attention is now called tothe fact that the passage of which plate G forms a swinging wall has aninlet e, Fig. l, of substantially the area of the Hue A; while, when theplate G is in the position shown in dotted lines, Figs. l. and 3, thearea of the then existing outlet o is less than that of inlet e. As thecross sectional area of the passage from inlet c to the escape outlet adecreases, the velocity o-f the gas current is increased. Hence v theinertia of the projected solid particles is increased. As this increasevaries as the square of the velocity, and as the resistance of theprojected particles to any force tending to change their direction oftravel varies as the inertia, the result is a very eHective trapping ofthe particles by the water.

Tests made by us upon an actual apparatus constructed substantially inaccordance with our present disclosure show that it is possible to makethe velocity.Y of the gases at theescape outlet a orpoint of projectionof the particles from two to eight times greater than the ordinaryvelocity of travel of gases in boiler Hues, and still not seriouslyaffect the draft.

It will be observed that the cross sectional area of the funnel-shapedpassage bounded by plate G is gradually reduced so that the velocity ofthe particles before projection will be gradually increased. ln actualpractice, we find that the length of said passage may be from two to tenfeet, but it is better to make it as long as possible so that theparticles mty be carried gradually to a velocity at the outlet a,relatively much higher than that which they have in Hue A.

ln many steam power plants, the quantity f escape ltime. When the boileris running at double rating, approximately twice as much gas will bedelivered from 4flue A. In using our apparatus in such circumstances,the swinging plate G is normally set in a selected position which givesan outlet area a to produce a certaln escape velocity of the particlessuitable to a certain rating-say the position shown in full lines inFig. 1. If the rating is augmented-say doubledthen the pawl and ratchetmechanism N released and the plate G is permitted to swing to anotherposition whereby the escape area a is increased to a suiiiciently toreduce the velocity to that previously chosen-say the positionshown indotted lines in Figs. l and 3; or in other words, by suitably adjustingthe escape area at a, as the rating of the boiler is exceeded, we mayvary the velocity of the particles at their point of projection orescape orifice.

In cases where the velocity of the current in the flue varies,especially when forced draft is used, it may be desirable not only tovary the area of the outlet a, but also to vary the interval d or lengthof the projected jet of particles between said outlet and the liquidlevel. Said interval should not be less 1n area than the area of outleta. On the other hand, it is desirable to make it as small as possible.Let it now be assumed, for purposes of present explanation, that theplate G and the pipe section T are Vin the positions shown in dottedlines. The corresponding water level is then at b. When the velocity ofthe iiue current falls off, the handle M is operated to brin the plate Ginto the position shown in full ines, thus reducing the area of outletfrom a to a, and increasing the velocity. The interval at d frompartition G to level Z) may be di,- minished by raising the water tolevel c. This is effected as already explained, with an increase in thetrapping efficiency.

Tests made by us with this apparatus applied to four 650 H. P. boilershave shown that ninety-two per cent. of the cinders or flue dustdelivered to the apparatus was trapped in the water, and preventedfrompassing to the chimney.

In order to remove the accumulated cinders or like material from thetank E, we provi-de a branch pipe U from the water supply pipe O whichhas several inlets V into said tank. Similar outlets are provided on theopposite side of the tank which communicate with a settling vessel W.When it is desired to clean out the tank, the gas current from the flueA is shut ofi", the valve R in pipe P is closed to cut od the watersupply, and the valve X in pipe U is opened. The water entering theseveral inlets V sweeps the solid material to the outlets, and saidmaterial is collected and drained in the settling vessel W.

We claim:

l. The method of trapping solid particles in suspension in a gas currentwhich consists in projecting said particles in a directionnormal to andupon the surface of a body of liquid and varying the velocity of saidparticles at their point of projection.

2. The method of trapping solid particles in suspension in a gas currentwhich consists in projecting said particles in a direction normal to andupon the surface of a body of liquid and varying the velocity of saidparticles at their oint of projection, and delivering a liquid currentinto said particles before they reach said liquid surace.

3. The method of trapping solid particles in suspension in a gas currentof varyinfr velocity which consists in projecting said particles in adirection normal to and upon the surface of a body of li uid, andvarying the velocity of said partie es at their point of projectioncorrespondingly to the variations of said current.

4. The method of trapping solid particles in suspension in a gas currentwhich consists in projecting said suspended particles in a directionnormal to and upon the surface of a body of liquid, varying the velocityof discharge of said particles at their point of projection, andsimultaneously varying the interval between said point of projection andsaid liquid surface.

In testimony whereof we have affixed our signatures in presence of twowitnesses.

THOMAS E. MURRAY. CHARLES B. GRADY.

Witnesses:

GERTRUDE T. PORTER, MAY T. MCGARRY.

